Trees, resinous, usually tall, with crowns becoming sympodial, often emergent, all at first monopodial and a few remaining so, some or most parts hairy, hairs mostly unicellular, acicular and usually fascicled or stellate, peltate or emarginate and single; frequently also with more or less caducous, multicellular, long-stalked (Vateria) or capitate (Dipterocarpus) hairs. Leaves simple, alternate, entire or rarely sinuate-cre-nate, usually coriaceous, penninerved, frequently with domatia in the axils of nerves; stipules small, deciduous. Flowers bisexual, regular, pentamerous, usually sweet-scented, in axillary or terminal racemes or panicles; bracts minute or absent, rarely larger and persistent. Calyx lobes free; imbricate or rarely subvalvate, frequently united into a short or long tube, free or adnate to the ovary, becoming enlarged and wing-like in fruit. Corolla contorted, lobes free or often connate at base, twisted in bud. Stamens 5, 10, 15 or numerous, variously connate or free; filaments usually short and often dilated at base; anthers bilocular, latrorse or rarely endporous; connective aristate or with an obtuse appendage. Ovary superior or semi-inferior (Dipterocarpus), 2- or 3-locular, ovules 2 in each locule, anatropous or pendulous; styles columnar, entire or trifid, frequently on a stylopodium; stigma small, obscure, 3 - 6-lobed. Fruit an indehiscent nut or a 3-valved capsule with persistent calyx more or less enclosing it, or reflexed, often with some of the lobes accrescent into contorted linear wings. Seeds exalbuminous, cotyledons fleshy, equal or unequal, straight or more or less plaited and crumpled.
Confined to Asian tropics except for a few species in Tropical Africa, mostly in the
humid zone, ca 15 genera and 580 species; ca 5 genera and 30 species in India.
Notes.
Dipterocarps, in general are large evergreen trees with tall branchless stems and do not flower or set seed until they have attained large size and considerable age with the exception of the Vatica species which are shrubs or small trees and flower at an early stage. The species belonging to Dipterocarpus and Hopea are wholly evergreen and are found in the tropical evergreen forests.
Shorea species stand on the border line between the evergreen and the deciduous forests, attaining the former state in very moist fertile localities and the latter state in less moist or dry situations. Majority of the dipterocarps belong to the hygrophilous type, while some like Shorea spp., Dipterocarpus costatus Gaertn.f. belong to the xerophilous type. The dipterocarps occur in India in three zones, viz. Eastern India, Peninsular India and the Andaman and Nicobar Islands. The northern and central part of India is represented by only one species that is Shorea robusta Roxb. ex Gaertn.f.
Literature.
ASHTON, P.S. (1982). Dipterocarpaceae. In: STEENIS, C.G.G.J. VAN, Fl. Males. 1, 9(2): 237-552; In: DASSANAYAKE, M.D. & F.R. FOSBERG (1980). Rev. Handb. Fl. Ceylon 1: 364 - 423 and FAO Reg. off. Asia & Pacific; (1985) Dipterocarps of S. Asia, RAPA monogr. 4: 1 - 321.SMITINAND et al (1979). The Manual of Dipterocarpaceae of mainland S.E. Asia. Thai For. Bull. 12: 1 - 133.
KEY TO THE GENERA
1a. Leaves plicately folded in bud; stipules amplexicaul, stipular scars encircling twigs; calyx tubular with
short lobes
b. Leaves, stipules and stipular scars not as above; calyx lobes nearly free
2
2a. Fruit sepals imbricate with a thickened saccate base, appressed to the nut; anthers with long awns (except in Shorea robusta and S.tumbuggaia)
3
b. Fruit sepals valvate, without thickened base; awns of the anther short or none
4
3a. Leaf nervation dryobalanoid or subdryobalanoid; petals not exceeding 6 mm long; stamens usually 10 or 15; fruiting calyx with 2 aliform and 3 short sepals, each enlarged calyx lobe (wing) with 5 or more fine veins from the base
b. Leaf venation not as above; petals ca 9 mm long; stamens 15 or more; fruiting calyx with 3 aliform and
2 short sepals, rarely 5, all aliform or short, each enlarged lobe (wing) with 10 or more fine veins from
the base
